1. Field of the Invention
The present invention relates to couplers for joining the ends of successive lengths of pipe or conduit and/or connecting a pipe or conduit to a housing or other mounting surface wherein the connection will be exposed to axial transverse and bending vibrations. In particular, the present invention relates to couplers for joining pipes to one another or to other structures in exhaust systems for vehicles.
2. The Prior Art
It is well known that, in vehicle exhaust systems, particularly those for passenger vehicles which have high vibration engines, such as diesel vehicles, and heavy duty vehicles, such as large trucks or earth moving equipment, the internal combustion (i.c.) engines produces significant amount of vibration in the exhaust system. Operation of the motors at continuous speeds for prolonged periods of time can, especially, produce what are known as harmonic vibrations which can cause significant deflections in extended lengths of exhaust pipe and at locations where such pipes are mounted to structures such as brackets, engine manifolds, and the like. Repeated deflections and vibration along the exhaust pipe system can, in turn, cause the structures to weaken with time and ultimately fail. Further, such harmonic vibrations can also be transmitted through the exhaust pipes to the mountings of the pipes, promoting the loosening of the mountings, which can result in the sudden displacement of one or more components of the exhaust system, with the potential for both personal injury and equipment damage.
In addition to the vibrations caused by the operation of the motor of the vehicle, an exhaust system is also subjected to various tension, compression and bending forces which also arise during the operation of the vehicle. While individual exhaust system components could be made stronger and more massive to resist failure by fatigue, such constructions would be undesirable due to weight considerations. Further, by making individual elements stiffer, the vibrations are merely transmitted throughout the exhaust system to the mountings or other components and are not reduced or eliminated. Accordingly, it is desirable to isolate the exhaust system, or at least components of the system, from such vibrations and forces.
It is known that if the pipes of an exhaust system are divided and separated by non-rigid connections, rather than being constructed as continuous extended lengths, the development of harmonic vibrations from the motor is precluded or reduced. Such non-rigid connections can be advantageously employed to absorb other tension, compression and bending forces, apart from and in addition to the motor vibration.
It is therefore desirable to provide a coupler for joining a length of exhaust pipe, to another pipe or to a mounting, such as an engine manifold, which coupler joins the components in a non-rigid fashion and is capable of absorbing tension, compression, and bending forces, as well as the vibrational forces, without transmitting them from one exhaust system component to another.
An example of a prior art coupler is found in Usui, U.S. Pat. No. 4,792,161. In Usui, a pair of concentrically arranged spring coils are utilized to provide a mechanical connection between the pipes to be joined. One drawback of the coupler in Usui is that when the coils are in a stretched or bent configuration, gaps may form between individual bights of the coil, into which dirt, debris and moisture may invade, which may interfere with the operation of the coils through abrasion, rusting and so forth. In addition, the coils (which are arranged one threaded within the other) are unprotected and exposed to the elements at all times, and are thus susceptible to damage from abrasion and other harmful physical contact. A further drawback of the coupler apparatus of Usui is that a sealing ring positioned between the overlapping pipe ends, is relied upon to provide sealing means to prevent escape of the exhaust gases. The sealing ring is subjected to cyclical flexure, tension and compression forces which will ultimately comprise the seal and require replacement of the coupler.
Yet another prior art coupler apparatus is disclosed in Udell, U.S. Pat. No. 5,145,215. In Udell an inner sleeve member is concentrically received by an outer sleeve member. A substantially porous, non-sealing, vibration absorbing spacer member is arranged between the sleeve members where they overlap, to preclude direct contact between the sleeve members. The spacer member is non-sealing to preclude deterioration while minimizing interference with the reciprocation and articulation of the sleeve members. A flexible, extensible bellows member mechanically connects the sleeve members and at their distant, non-overlapped ends. A closure member, typically a braided metal wire, surrounds the bellows member for protecting the extensible bellows member for protecting the extensible bellows member from damage from external elements and forces.
While the apparatus of the Udell patent is capable of accommodating some extension, compression, and relative pivoting of the pipe ends or other fluid transmission members which are connected, the Udell apparatus is provided only with a single "resilient" single spacer member which is positioned axially and radially between radially extending flanges of the respective overlapping pipe ends. While the bellows member is capable of axial extension and compression as well as some bending to accommodate the movements of the respective overlapped pipe ends, the bellows member is not configured for providing a progressive resistance to either compression or extension of the coupler apparatus so as to tend to maintain the respective components of the coupler apparatus in a neutral configuration.
The "resilient" spacer member, being constructed of compressed steel wire mesh does not provide significant graduated damping of or progressive resistance to the axially directed vibrational forces when such forces are sufficiently strong to cause the connector to be compressed to an extreme orientation. In the possible, though typically uncommon, event of overcompression of the coupler, there is a possibility of jamming or distortion of components, which may adversely effect the subsequent performance of the coupler, and may even lead to premature degradation and/or failure of the coupler. There is no graduated damping mechanism to help resist and lessen the impact of such jamming forces.
It is desirable to provide a flexible coupler apparatus which has an enhanced, more robust configuration in order to provide for the decoupling of an exhaust system from a source of vibration, such as an internal combustion engine.
It is also desirable to provide a flexible coupler apparatus which is provided with a structure which will provide for the graduated damping of forces when such force is being imposed upon the coupler could result in overcompression or overextension of the flexible coupler apparatus.
It is further desirable to provide a flexible coupler apparatus which is provided with structure which will tend to restore the respective components of the coupler apparatus to a neutral configuration following rebound from any individual flexural, tensile or compressive force.
These and other objects of the invention will become apparent in view of the present specification including claims, and drawings.